MEMS RF switch module including a vertical via

ABSTRACT

An apparatus and method to provide a micro-electromechanical systems (MEMS) radio frequency (RF) switch module with a vertical via. The MEMS RF switch module includes a MEMS die coupled to a cap section. The vertical via passes through the cap section to electrically couple an RF switch array of the MEMS die to a printed circuit board (PCB). In one embodiment, the MEMS die includes a trace ring surrounding at least a portion of the RF switch array so that a signal may enter or exit the MEMS RF switch module using the vertical via without crossing the trace ring.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates generally to micro-electromechanicalsystems (MEMS) and, more specifically, the present invention relates toa MEMS switch module including a vertical via.

2. Background Information

Micro-electromechanical systems (MEMS) devices have a wide variety ofapplications and are prevalent in commercial products. One type of MEMSdevice is a MEMS RF switch module. A typical MEMS RF switch modulecontains one or more MEMS switches arranged in an RF switch array. MEMSRF switch modules are ideal for wireless devices because of their lowpower characteristics and ability to operate in radio frequency ranges.MEMS RF switch modules are often found in cell phones, wireless computernetworks, communication systems, and radar systems. In wireless devices,MEMS RF switch modules can be used as antenna switches, mode switches,and transmit/receive switches.

Typically, MEMS devices, such as MEMS RF switch modules, use electricalfeed-throughs that emerge horizontally from the edges of the module.These horizontal feed-throughs allow electrical signals to enter andexit the module. However, horizontal feed-throughs increase thefootprint size of the MEMS module. Additionally, routing signalshorizontally often results in crossing signal lines. Also, horizontalfeed-throughs affect electrical performance, such as insertion loss,because of the length of the signal paths.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention is illustrated by way of example and notlimitation in the accompanying figures.

FIG. 1 is a cross-sectional view diagram illustrating one embodiment ofa MEMS RF switch module in accordance with the teachings of the presentinvention.

FIG. 2A is a top view diagram illustrating one embodiment of a MEMS diein accordance with the teachings of the present invention.

FIG. 2B is a top view diagram illustrating one embodiment of a capsection in accordance with the teachings of the present invention.

FIGS. 3A and 3B are top view diagrams illustrating alternativeembodiments of MEMS RF switch modules in accordance with the teachingsof the present invention.

FIG. 4 is a top view diagram illustrating one embodiment of a MEMS RFswitch module in accordance with the teachings of the present invention.

FIG. 5 is a top view diagram illustrating one embodiment of a MEMS RFswitch module in accordance with the teachings of the present invention.

FIG. 6 is a top view diagram illustrating one embodiment of a MEMS RFswitch module in accordance with the teachings of the present invention.

FIG. 7 is a top view diagram illustrating one embodiment of a MEMS RFswitch module in accordance with the teachings of the present invention.

FIG. 8 is a top view diagram illustrating one embodiment of a MEMS RFswitch module in accordance with the teachings of the present invention.

FIG. 9 is a schematic diagram illustrating one embodiment of a wirelessdevice including a MEMS RF switch module in accordance with theteachings of the present invention.

DETAILED DESCRIPTION

Methods and apparatuses to provide MEMS RF switch modules havingvertical vias are disclosed. In the following description numerousspecific details are set forth in order to provide a thoroughunderstanding of the present invention. It will be apparent, however, toone having ordinary skill in the art that the specific detail need notbe employed to practice the present invention. In other instances,well-known materials or methods have not been described in detail inorder to avoid obscuring the present invention.

Reference throughout this specification to “one embodiment” or “anembodiment” means that a particular feature, structure or characteristicdescribed in connection with the embodiment is included in at least oneembodiment of the present invention. Thus, appearances of the phrases“in one embodiment” or “in an embodiment” in various places throughoutthis specification are not necessarily all referring to the sameembodiment. Furthermore, the particular features, structures orcharacteristics may be combined in any suitable manner in one or moreembodiments. In addition, it is appreciated that the figures providedherewith are for explanation purposes to persons ordinarily skilled inthe art and that the drawings are not necessarily drawn to scale.

Referring to FIG. 1, a MEMS RF switch module 100 in accordance with oneembodiment of the present invention is shown. It will be understood thata MEMS module is also referred to as a MEMS package by one skilled inthe art. A MEMS die 102 is coupled to a cap section 104. The MEMS die102 includes an RF switch array 124. The RF switch array 124 includes atleast one of, but is not limited to, a cantilever switch, a relay, orthe like. The cap section 104 includes, but is not limited to, silicon,ceramic, glass, plastic, or the like.

The MEMS RF switch module 100 is coupled to printed circuit board (PCB)106. Cap section 104 includes contacts 110 and 112 mounted to the bottomof the cap section 104. The contacts 110 and 112 are used toelectrically and physically couple the MEMS RF switch module 100 to PCB106 using various methods well known in the art. In the embodiment shownin FIG. 1, solder balls 114 and 116 are used to couple to the MEMS RFswitch module 100 to PCB 106.

MEMS RF switch module 100 includes vias 118 and 120 that pass throughthe cap section 104 to electrically couple the MEMS die 102 to contacts110 and 112, and subsequently to PCB 106. The vias 118 and 120 passvertically through the cap section 104. The term “vertical” describesthe vias 118 and 120 in relation to the mounting of the MEMS RF switchmodule 100 to PCB 106. The vias 118 and 120 allow signals to transitshort distances between the RF switch array 124 and PCB 106. Also, whilevias 118 and 120 are depicted in FIG. 1 as generally straight, they arenot limited to this configuration.

In one embodiment, the vias 118 and 120 are electroplated with a metalconductor. In another embodiment using a ceramic cap section 104, thevias are metal filled. In this embodiment, the fabrication begins with aceramic sheet, often called a “green sheet,” that is punched with holesaccording to a pre-defined pattern. Metal paste is stencil printed tofill in the holes. The entire piece is heated and cleaned to producemetal filled vias.

In the following discussion, reference will be made to FIGS. 2A and 2Bin conjunction with FIG. 1. FIG. 2A shows a top view of MEMS die 102.FIG. 2B shows a top view of cap section 104.

MEMS die 102 includes a seal ring 122A and the cap section 104 includesa seal ring 122B. When the MEMS die 102 and the cap section 104 arecoupled together, the seal rings 122A and 122B are pressed together toform a hermetical seal. The seal rings 122A and 122B can be sealed usingsolder, gold thermocompression bonding (TCB), gold thermosonic bonding(TSB), or the like. Thus, when the MEMS RE switch module 100 is sealed,the cavity around RE switch array 124 is sterile to reduce the affectsof dust and other contaminants on the performance of the RF switch array124. In one embodiment, the seal rings 122A and 1228 are metal. Inanother embodiment, only one of MEMS die 102 or cap section 104 includesthe seal ring prior to coupling MEMS die 102 and cap section 104together.

FIGS. 1, 2A and 2B depict pads 126A, 126B, 128A, and 128B. Pads 126A and126B electrically couple signals from the MEMS die 102 to contact 110 byway of via 118. Pads 128A and 128B electrically couple signals from theMEMS die 102 to contact 112 by way of via 120. In one embodiment, thepads 126A, 126B and 128A, 128B are physically coupled together using thesame technique as utilized to couple the seal rings 122A, 122B. It willbe understood that the invention is not limited to the design shown inFIGS. 1, 2A and 2B; in alternative embodiments, the MEMS RF switchmodule 100 may include other configurations of vias and pads.

A MEMS RF switch module with vertical vias offers several advantages.Feed-throughs that emerge vertically from the module reduce the formfactors of the module. For example, MEMS RF switch modules with verticalvias have form factors in the range of 2×2 mm compared to form factorsof 3×6 mm using conventional packaging schemes with horizontalfeed-throughs. Also, the ability to route signals vertically from themodule allows the route layout to be planar without any crossing signallines. This simplifies the design and construction process of the MEMSmodule. Additionally, vertically routing signals on and off the moduleusing vertical vias improves insertion loss since the signal paths aresignificantly shorter than typical horizontal routing schemes.

FIGS. 3A–8 illustrate alternative embodiments of MEMS RF switch moduleconfigurations. Referring to FIGS. 3A and 3B, a top view diagram of aMEMS RF switch module 300 in accordance with one embodiment of thepresent invention is shown. An input terminal 304 is electricallycoupled to the inputs of RF switch array 302. Output terminal 308 andactuation terminal 306 are electrically coupled to the outputs andactuation controls of RF switch array 302. The terminals 304, 306 and308 are each electrically coupled to vias (not shown) that passvertically through a cap section (not shown) to route signals verticallybetween the MEMS RF switch module 300 and a PCB (not shown.)

The MEMS RF switch module 300 also includes a trace ring 301. In oneembodiment, trace ring 301 surrounds a portion of the RF switch array302, while in another embodiment, the trace ring 301 surrounds theentire RF switch array 302. The input terminal 304 and the inputs of theswitches of the RF switch array 302 are electrically coupled to thetrace ring 301.

The vertical via scheme in conjunction with the trace ring 301 optimizesthe performance of MEMS RF switch module 300. The vertical vias allow asignal to enter or to exit module 300 without crossing or “breaking” thetrace ring 301. Eliminating the crossing of signal lines, such as RFsignal lines, improves the electrical performance of the MEMS RF switchmodule 300. The vertical via design also shortens the signal path that asignal must transit between the RF switch array 302 and a PCB coupled tothe MEMS switch module 300.

In FIGS. 3A and 3B, the input terminal 304 is electrically coupled tothe trace ring 301. It will be understood that the MEMS RF switch module300 is not limited to this configuration. On or more of the terminals304, 306, and 308, or any combination thereof, may be electricallycoupled to the trace ring 301. In FIG. 3A, the actuation terminal 306 ispositioned near the input terminal 304; while in FIG. 3B, the actuationterminal 306 is positioned near output terminal 308. The vertical viascheme offers the flexibility to easily configure the electricalfeed-throughs as needed for a particular design without the difficultyand performance losses associated with horizontal feed-throughs.

It will be understood that the terminals 304, 306, and 308 areelectrically coupled to RF switch array 302 by multi-line routes. Theterminals 304, 306, and 308 provide for signals to be routed toparticular switches in the RF switch array 302. Thus, switches of the RFswitch array 302 may be operated on an individual basis. For example, RFswitch array 302 may include “series” switches to control the main RFsignal and “shunt” switches to ground a receiver during the transmittime.

Referring to FIG. 4, a top view diagram of a MEMS RF switch module 400in accordance with one embodiment of the present invention is shown. Aninput terminal 404, an output terminal 408, and an actuation terminal406 are each electrically coupled to RF switch array 402. The terminals404, 406, and 408 are each electrically coupled to vias (not shown) thatpass vertically through a cap section (not shown) to route signalsvertically between the module 400 and a PCB (not shown.) A trace ring401 surrounds the RF switch array 402 and is electrically coupled to theoutputs of the RF switch array 402 and the output terminal 408.

FIG. 5 is a top view diagram of a MEMS RF switch module 500 that is analternative embodiment of MEMS RF switch module 400 described above.Module 500 adds to module 400 an input terminal 505 coupled to an RFswitch array 502 and an actuation terminal 507 coupled to RF switcharray 502. MEMS RF switch module 500 also includes a trace ring 501surrounding the RF switch array 502 and electrically coupled to theoutputs of the RF switch array 502 and output terminal 408.

Referring to FIG. 6, a top view diagram of a MEMS RF switch module 600in accordance with one embodiment of the present invention is shown. Aninput terminal 604 is electrically coupled to RF switch array 602.Output terminal 608 and actuation terminal 606 are each electricallycoupled to the RF switch array 602. The terminals 604, 606 and 608 areeach electrically coupled to vias (not shown) that pass verticallythrough a cap section (not shown) to route signals vertically betweenthe module 600 and a PCB (not shown.) A trace ring 601 surrounds the RFswitch array 602 and is electrically coupled to the outputs of the RFswitch array 602 and output terminal 608.

MEMS RF switch module 700, shown in FIG. 7, is an alternative embodimentof the present invention. Module 700 includes the elements discussedabove in conjunction with module 600. MEMS RF switch module 700 alsoincludes an input terminal 705 electrically coupled to an RF switcharray 702 and an actuation terminal 707 electrically coupled to RFswitch array 702. MEMS RF switch module 700 includes a trace ring 701that surrounds the RF switch array 702 and is electrically coupled tothe outputs of the RF switch array 702 and output terminal 608.

Referring to FIG. 8, a top view diagram of a MEMS RF switch module 800in accordance with one embodiment of the present invention is shown. Aninput terminal 804 is electrically coupled to the inputs of RF switcharray 802 by a trace ring 801 that surrounds the RF switch array 802.The output terminal 808 and an actuation terminal 806 are eachelectrically coupled to the RF switch array 802. The terminals 804, 806and 808 are each electrically coupled to vias (not shown) that passvertically through a cap section (not shown) to route signals verticallybetween the module 800 and a PCB (not shown.) It should be noted thatsignals may enter and exit the MEMS RF switch module 800 using terminals804, 806 and 808 without crossing trace ring 801 because of the verticalvia design.

FIG. 9 shows a wireless device 900 in accordance with one embodiment ofthe present invention. The wireless device 900 includes a MEMS RF switchmodule 902 electrically coupled to an amplifier 904. An antenna 906 anda controller 908 are also electrically coupled to MEMS RF switch module902. The RF MEMS switch module 902 includes at least one vertical via asdescribed above.

In one embodiment, an RF signal is inputted into amplifier 904. The RFsignal is sent from the amplifier 904 to the MEMS RF switch module 902.The controller 908 inputs an actuation signal to the MEMS RF switchmodule 902 to actuate the switches of an RF switch array inside the MEMSRF switch module 902. The RF signal is routed through the MEMS RF switchmodule 902 to the antenna 906 for transmission.

In the foregoing detailed description, the method and apparatus of thepresent invention have been described with reference to specificexemplary embodiments thereof. It will, however, be evident that variousmodifications and changes may be made thereto without departing from thebroader spirit and scope of the present invention. The presentspecification and figures are accordingly to be regarded as illustrativerather than restrictive.

1. An apparatus, comprising: a micro-electro-mechanical system (MEMS)die including at least one MEMS device and one or more MEMS contactselectrically coupled to the at least one MEMS device; a cap coupled tothe MEMS die to form an enclosure around the at least one MEMS device,the cap including one or more internal contacts, each internal contactbeing electrically coupled to a corresponding external contact by a viaextending through the cap, wherein at least one of the internal contactscan be electrically coupled to at least one of the one or more MEMScontacts; and a trace ring disposed within the enclosure and coupled tothe at least one MEMS device, wherein one of an input terminal or anoutput terminal for the at least one MEMS device is coupled to the tracering.
 2. The apparatus of claim 1 wherein the at least one MEMS devicecomprises a radio frequency (RF) switch array including at least oneswitch.
 3. The apparatus of claim 1 wherein the one or more MEMScontacts include an input terminal, an output terminal, and an actuationterminal.
 4. The apparatus of claim 3 wherein the input terminal iselectrically coupled to a first internal contact, the output terminal iselectrically coupled to a second internal contact, and the actuationterminal is electrically coupled to a third internal contact.
 5. Theapparatus of claim 1 wherein the trace ring surrounds at least a portionof the at least one MEMS device to allow a signal to transit the MEMSmodule using at least one of the vias without crossing the trace ring.6. The apparatus of claim 1, further comprising a seal ring to couplethe cap to the MEMS die such that the cap and the die sealingly enclosethe at least one MEMS device.
 7. The apparatus of claim 1, furthercomprising a printed circuit board (PCB) coupled to at least one of theexternal contacts.
 8. The apparatus of claim 1 wherein at least one ofthe one or more internal contacts is a contact pad.
 9. An apparatuscomprising: a MEMS die including an array of MEMS radio frequency (RF)switches and one or more MEMS contacts electrically coupled to at leastone of the switches in the array; a cap coupled to the MEMS die to forman enclosure around the array, the cap including one or more internalcontacts, each internal contact being electrically coupled to acorresponding external contact by a via extending through the cap,wherein at least one of the internal contacts can be electricallycoupled to at least one of the one or more MEMS contacts; and a tracering disposed within the enclosure and coupled to the array, wherein oneof the input terminal or the output terminal is coupled to the tracering.
 10. The apparatus of claim 9 wherein the cap is coupled to theMEMS die by a seal ring.
 11. The apparatus of claim 9 wherein the capcomprises Silicon.
 12. The apparatus of claim 9 wherein the capcomprises a ceramic material.
 13. The apparatus of claim 9 wherein theone or more MEMS contacts comprise: an input terminal electricallycoupled to at least one switch in the array; an output terminal coupledto at least one switch in the array; and an actuation terminalelectrically coupled to at least one switch in the array.
 14. Theapparatus of claim 13 wherein the input terminal is electrically coupledto a first internal contact, the output terminal is electrically coupledto a second internal contact, and the actuation terminal is electricallycoupled to a third internal contact.
 15. The apparatus of claim 13wherein the MEMS die comprises a second MEMS RF switch arrayelectrically coupled to a second input terminal and to a secondactuation terminal, the second RF switch array electrically coupled tothe output terminal.
 16. The apparatus of claim 9 wherein the trace ringsurrounds at least a portion of the array to allow a signal to transitthe array using at least one of the vias without crossing the tracering.
 17. The apparatus of claim 9, further comprising a printed circuitboard (PCB) electrically coupled to at least one of the externalcontacts.
 18. The apparatus of claim 9 wherein at least one of the oneor more internal contacts is a contact pad.